Testing hypotheses about individual variation in plasma corticosterone in free-living salamanders

Thomas, Jessica R.; Magyan, Andrew J.; Freeman, Peter E.; Woodley, Sarah K.

doi:10.1242/jeb.149765

Cited by 8 publications

(3 citation statements)

References 81 publications

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“…Our results do not align with a previous study in free-living plethodontid salamanders (Desmognathus ochrophaeus) in which seasonal elevations in plasma CORT were associated with decreases in lymphocyte populations [74]. However, our results are consistent with results in captive D. ochrophaeus where physiological elevations in CORT (via dermal CORT treatment or handling stressor) did not affect leucocyte ratios, thereby, suggesting that the relationship between CORT and leucocytes may be context-dependent [42].…”

Section: (B) No Effect Of Corticosterone On Neutrophil To Lymphocyte ...contrasting

confidence: 99%

Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens )

Pereira

Bletz

McCartney

et al. 2023

Phil. Trans. R. Soc. B

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The amphibian chytrid fungus, Batrachochytrium salamandrivorans ( Bsal ) threatens salamander biodiversity. The factors underlying Bsal susceptibility may include glucocorticoid hormones (GCs). The effects of GCs on immunity and disease susceptibility are well studied in mammals, but less is known in other groups, including salamanders. We used Notophthalmus viridescens (eastern newts) to test the hypothesis that GCs modulate salamander immunity. We first determined the dose required to elevate corticosterone (CORT; primary GC in amphibians) to physiologically relevant levels. We then measured immunity (neutrophil lymphocyte ratios, plasma bacterial killing ability (BKA), skin microbiome, splenocytes, melanomacrophage centres (MMCs)) and overall health in newts following treatment with CORT or an oil vehicle control. Treatments were repeated for a short (two treatments over 5 days) or long (18 treatments over 26 days) time period. Contrary to our predictions, most immune and health parameters were similar for CORT and oil-treated newts. Surprisingly, differences in BKA, skin microbiome and MMCs were observed between newts subjected to short- and long-term treatments, regardless of treatment type (CORT, oil vehicle). Taken together, CORT does not appear to be a major factor contributing to immunity in eastern newts, although more studies examining additional immune factors are necessary. This article is part of the theme issue ‘Amphibian immunity: stress, disease and ecoimmunology’.

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Section: (B) No Effect Of Corticosterone On Neutrophil To Lymphocyte ...contrasting

confidence: 99%

Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens )

Pereira

Bletz

McCartney

et al. 2023

Phil. Trans. R. Soc. B

Self Cite

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“…Analyses of CORT in plethodontids have largely dealt with physiological (rather than developmental) responses in paedomorphic adults (Gabor et al 2016) and terrestrial adults (Wack et al 2013; Thomas et al 2017). Recent experiments indicate synergistic influences of CORT on T 3 -induced metamorphosis in Eurycea tynerensis , (R.M.…”

Section: Is the Metamorphic Response To Thyroid Hormones And Corticosmentioning

confidence: 99%

How Metamorphosis Is Different in Plethodontids: Larval Life History Perspectives on Life-Cycle Evolution

2017

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Plethodontid salamanders exhibit biphasic, larval form paedomorphic, and direct developing life cycles. This diversity of developmental strategies exceeds that of any other family of terrestrial vertebrate. Here we compare patterns of larval development among the three divergent lineages of biphasic plethodontids and other salamanders. We discuss how patterns of life-cycle evolution and larval ecology might have produced a wide array of larval life histories. Compared with many other salamanders, most larval plethodontids have relatively slow growth rates and sometimes exceptionally long larval periods (up to 60 mo). Recent phylogenetic analyses of life-cycle evolution indicate that ancestral plethodontids were likely direct developers. If true, then biphasic and paedomorphic lineages might have been independently derived through different developmental mechanisms. Furthermore, biphasic plethodontids largely colonized stream habitats, which tend to have lower productivity than seasonally ephemeral ponds. Consistent with this, plethodontid larvae grow very slowly, and metamorphic timing does not appear to be strongly affected by growth history. On the basis of this, we speculate that feeding schedules and stress hormones might play a comparatively reduced role in governing the timing of metamorphosis of stream-dwelling salamanders, particularly plethodontids.

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“…The effects of CORT on anuran immunity are complex and depend not only on the temporal pattern of GC release, but also interaction with several other aspects, such as life-history stage and individual body condition. For instance, within the reproductive season anuran males with higher plasma CORT levels display a higher number of leucocytes in the bloodstream [23,24]. Calling rate in anuran males is positively correlated with CORT plasma levels and with higher plasma BKA [25].…”

Section: Introductionmentioning

confidence: 99%

Contrasting effects of transdermal and implant corticosterone treatments in the American bullfrog wound healing

Madelaire

Silva

Titon

et al. 2023

Phil. Trans. R. Soc. B

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Glucocorticoid (GC) release is triggered by adverse stimuli that activate the hypothalamus-pituitary-adrenal/interrenal axis. Glucocorticoids may enhance or suppress immune functions depending on the level of elevation. In this study, we investigated the effects of transient and chronic increase of corticosterone (CORT) on the wound healing of the American bullfrog. Frogs were submitted to a daily transdermal hormonal application that acutely elevated CORT plasma levels, or vehicle as a control. Other frogs were surgically implanted with a silastic tube filled with CORT that resulted in chronic elevation of CORT plasma levels or received empty implants as a control. A dermal biopsy was performed to create a wound and was photographed every 3 days. Individuals treated with transdermal CORT started healing faster than their control 32 days after the biopsy. Frogs that received CORT implants tended to heal slower than control subjects. Plasma bacterial killing ability was not affected by treatment, which reinforces the constitutive nature of this innate immune trait. By the end of the experiment, frogs from the acute CORT treatment had smaller wounds compared with those receiving the CORT-filled implants, highlighting the differential effects of acute (immunoenhancing) and chronic (immunosuppressive) elevation of CORT plasma levels. This article is part of the theme issue ‘Amphibian immunity: stress, disease and ecoimmunology’.

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Testing hypotheses about individual variation in plasma corticosterone in free-living salamanders

Cited by 8 publications

References 81 publications

Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens )

Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens )

How Metamorphosis Is Different in Plethodontids: Larval Life History Perspectives on Life-Cycle Evolution

Contrasting effects of transdermal and implant corticosterone treatments in the American bullfrog wound healing

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